1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying apparatus of a recording apparatus of an electrophotographic process, adapted for use of a waste toner carrying apparatus which carries a waste toner, discharged from an image forming mechanism, to a recovery portion.
2. Related Background Art
In an image forming apparatus for example of an electrophotographic method of transfer type, a waste toner, which is not transferred from a photosensitive member to a recording material or an intermediate transfer belt but is discharged, remains in a cleaning device for the photosensitive member, though it is not illustrated.
For disposing of the waste toner accumulating in the cleaning device, various means and configurations are conceived as follows:
1) In case the image forming apparatus has a detachable process cartridge which including a developing device and a cleaning device, the waste toner may be stored in the cleaning device, by designing in advance a volume for containing the waste toner in the cleaning device so as to match the total amount of the waste toner generated until the process cartridge reaches an end of the service life thereof.
The process cartridge is considered to reach the end of its service life when toner of a predetermined amount, filled in advance in a developing toner hopper associated with the developing deice, is exhausted and is replaced by a new process cartridge.
2) Also in a process cartridge, Japanese Patent Application Laid-open No. 09-281866 proposes a configuration of providing a waste toner containing portion in the developing toner hopper in which a vacant space is progressively generated with the consumption of the toner, and feeding the waste toner in the cleaning device into the waste toner containing portion in the developing toner hopper, thereby decreasing the waste toner containing volume in the cleaning device and reducing the entire dimension of the process cartridge.
In such configuration, for feeding the waste toner from the cleaning device to the waste toner containing portion in the developing toner hopper, a waste toner outlet of the cleaning device and a waste toner containing portion in the developing toner hopper are connected, as shown in FIGS. 15A and 15B, by a curved tube 41 incorporating a flexible screw 40 which is formed by a spiral portion only without an axis, thereby forming an upward waste toner carrying path from the cleaning device to the waste toner containing portion in the developing toner hopper. A waste toner inlet 42 is formed in the curved tube 42 at a lateral end of the cleaning device, and the waste toner discharged from the waste toner outlet of the cleaning device drops and is charged into the curved tube 42 from the aforementioned waste toner inlet 42. The waste toner is carried and scooped up, by a rotation of the flexible screw 40, in the curved tube 41 toward the waste toner containing portion provided in the developing toner hopper.
3) Japanese Patent Application Laid-open No. 08-54808 proposes a configuration, in a photosensitive member or a process cartridge containing a photosensitive member, rendered detachable from a main body of the image forming apparatus, of utilizing an internal cavity of the photosensitive member as a waste toner container and feeding the waste toner from the cleaning device in succession into the internal cavity of the photosensitive member. More specifically, a waste toner outlet of the cleaning device and a rotary central axis of a cylindrical photosensitive member are connected with a curved tube incorporating a flexible screw, thereby forming an upward waste toner carrying path from the cleaning device to the internal cavity of the photosensitive member. Thus the waste toner is fed from the cleaning device to the internal cavity of the photosensitive member by a rotation of the flexible screw.
Also Japanese Patent Application Laid-open No. 04-116869 discloses a configuration of utilizing plural carrying tubes and carrying the waste toner upward to a waste toner container positioned above a joint portion of the carrying tubes.
Toner employed in an image forming apparatus for example of an electrophotographic process has a sufficient fluidity in a state before use, thus rarely forming agglomerates. Also the fluidity is stable and scarcely shows a difference resulting from a different in the environmental condition or in the lot. However, waste toner, that has once passed an image forming process, shows properties different from those of the toner before use, because of a decomposition of filler or a mixing of paper dust. More specifically, the fluidity decreases significantly, and a carrying property by carrying means such as a screw is also significantly lowered. It also forms agglomerates more easily, thus significantly increasing the frequency of solidifying in the carrying path, thereby locking the carrying means. Also as the waste toner is unstable in the composition for example by the mixing of paper dusts, the waste toner may fluctuates significantly in the fluidity and is very difficult to handle in the carrying means.
A waste toner carrying apparatus utilizing a flexible screw, as described in Japanese Patent Application Laid-open Nos. 09-281866 and 08-54808 allows forming a curved carrying path. However, in case the waste toner carrying path is bent excessively, or is relatively long with an upward carrying, or in case the amount of the carried waste toner is excessively large, the waste toner forms agglomerates in the carrying path because of the deteriorated carrying property of the waste toner, thereby increasing the frequency of locking the rotation of the flexible screw constituting the carrying means. Also, in case the external diameter of the flexible screw is made larger to increase the carrying capacity for the waste toner, the flexible screw loses flexibility and the carrying path inevitably results in a larger radius in the curvature thereof, thus hindering compact designing of the apparatus. Also, since the flexible screw carries the waste toner by rotation under friction with the internal wall of the tube or the pipe constituting the external wall, there results a concern for a loss of durability by abrasion in a contact portion between the flexible screw and the internal wall of the tube or the pipe. For obtaining a sufficient durability, which is the same as the service life of the apparatus, it is necessary to select a tube or a pipe resistant to abrasion, leading to a higher component cost.
Therefore, a process cartridge or an image forming apparatus disclosed in Japanese Patent Application Laid-open Nos. 09-281866 and 08-54808 realizes the configuration with the flexible screw, within limited conditions such as a suitable curvature of the carrying path, a suitable carrying path length, a suitable carrying amount of the waste toner, and a suitable durability.
However, in an image forming apparatus or a full-color image forming apparatus of toner replenishing type, it is required to stably carry the waste toner without clogging over a prolonged period despite of the deteriorated carrying property of such waste toner and also to stably carry a large amount of the waste toner, and, particularly in a full-color apparatus, the amount of the waste toner becomes very large because of the presence of four developing devices, and the aforementioned waste toner carrying apparatus utilizing the flexible screw is not adequate for collectively carrying all the waste toners upwards to a waste toner recovery container.
Therefore, in the image forming apparatus or the full-color image forming apparatus of a toner replenishing type, there is adopted a vertical layout configuration in which a waste toner recovery container is provided below a waste toner outlet of the developing device (vertical layout), whereby the waste toner discharged from the waste toner outlet of the cleaning device drops and is collected in the waste toner recovery container, or in which, even in case the waste toner discharged from the waste toner outlet of the cleaning device is carried to the waste toner recovery container by a waste toner carrying apparatus utilizing a hard carrying screw or a flexible screw, such carrying is executed through a downward carrying path, an inclined downward carrying path or a substantially horizontal linear carrying path.
However, in the full-color apparatus or a toner replenishing type, such vertical layout, in which the waste toner recovery container of a large capacity is positioned below the waste toner outlet of the cleaning device for recovering the discharge waste toner by dropping, is associated with a drawback of rendering the image forming apparatus itself bulky. Also in an image forming apparatus, it is required to limit the direction of access by the user or the service personnel for toner container replacement, process cartridge replacement, jam clearance or waste toner box replacement to only one direction in consideration of operability, and such direction is a front side of the image forming apparatus where the user is to be positioned.
In order to position the waste toner box at the front side of the image forming apparatus and to realize a compact configuration at the same time, it is necessary to adopt a layout in which the waste toner recovery container is positioned at the same height as the developing device etc., and for this purpose, there is required a waste toner carrying apparatus which is capable of carrying upwards the waste toner, discharged from a waste toner outlet of the cleaning device, to an upper aperture of a waste toner recovery container positioned at a same height as the developing device and also capable of continuing stable upward carrying without causing a clogging of the carrying path by the waste toner and without requiring a cleaning operation over a prolonged period extending to the lifetime of the main body of the image forming apparatus, and which is also compact and inexpensive.
Particularly in a full-color apparatus of a toner replenishing type, there is required compact and inexpensive waste toner carrying means capable of carrying the waste toners, discharged from four developing devices and a transfer belt cleaning device, collectively to a recovery container, also capable of continuing carrying without causing a clogging by the waste toner and without requiring a cleaning operation up to the lifetime of the main body of the image forming apparatus, and not requiring a drive source or a locking detection mechanism in plural units. Also in a full-color apparatus of toner replenishing type in which sheet paths are formed short in a vertical direction and four developing devices are positioned in an inclined arrangement, there is required a waste toner carrying apparatus in which a waste toner box is provided at the front side of the image forming apparatus thereby improving the replaceability of the waste toner box without an increase in the footprint of the apparatus.
However, in case of carrying the waste toner upwards by providing a screw in a carrying tube as described in Japanese Patent Application Laid-open No. 04-116869, the waste toner is difficult to carry at an upper connecting portion of the carrying tube because it is inclined upwards, and a mere connection of the carrying tubes results in a clogging of the toner at the connecting portion.
Also the toner transfer at the connecting portion of the carrying tubes is usually achieved by forming a connecting portion at a bottom face of the carrying tube and transferring the toner by the weight thereof to a downstream carrying tube, but, in case a connecting portion is formed at a side face of the carrying tube, the carrying power at such transfer portion becomes lower as the weight of the toner cannot be utilized for transfer to the carrying tube of the downstream side. On the other hand, an increase in the carrying power at such transfer portion may result in a toner clogging.